The invention relates generally to fuel injectors for gas turbine combustors, and, more specifically, to an improved fuel spray bar for an augmentor of a gas turbine engine.
In a gas turbine engine having an augmentor, or afterburner, disposed downstream of a gas generator for providing additional thrust when desired, fuel spraybars, or injectors, are utilized for injecting fuel into the augmentor to be mixed with gases discharged from the gas generator. Generally, it is desirable that the spraybars provide a fuel discharge port for about each square inch of augmentor combustion area, which therefore typically requires a large number of such spraybars.
One form of improved spray bar is disclosed in U.S. Pat. No. 2,978,870--Vdoviak, assigned to the present assignee, which includes a plurality of fuel tubes of different lengths for positioning fuel discharge orifices at radially different positions, as well as for providing additional benefits. A plurality of relatively short and long spraybars is typically circumferentially spaced around an augmentor liner to provide a relatively uniform discharge of fuel therein.
Gas turbine engine performance may be made to increase by increasing turbine gas temperatures, which increases the metal temperature of the spraybars subject to such turbine gases and increases the tendency for preignition of the fuel/gas mixture between the spray bar and the flameholders disposed downstream therefrom. Accordingly, the distance between the spraybars and the flameholders may be decreased to avoid the preignition tendency. However, decreasing this fuel mixing distance then requires increased lateral distribution of fuel from the spraybars in the relatively shorter distance between the spraybars and the flameholders to ensure a uniform dispersion of fuel at the flameholders.
Yet further, during "wet" operation of a conventional augmented engine fuel flows through the spraybar and thereby cools the spraybar. However, this cooling occurs only during such wet operation. In order to ensure a useful life of a spraybar operated under higher-than-conventional turbine exit gas temperatures and during "dry" (unaugmented) and low levels of wet operation of an augmented engine, cooling thereof may be utilized. However, undesirable thermal stress due to the interaction of the cooling fluid with the relatively hot spraybar should be avoided for obtaining a useful life thereof.
Accordingly, one object of the present invention is to provide a new and improved fuel spraybar for a gas turbine engine.
Another object of the invention is to provide a fuel spraybar for a gas turbine engine augmentor having means for cooling the spraybar to allow for increased gas temperatures in the gas turbine engine.
Another object of the invention is to provide a fuel spraybar for a gas turbine engine augmentor having means for cooling the spraybar which accommodates differential thermal expansion and contraction.
Another object of the invention is to provide a spraybar having means for laterally dispersing fuel.
Another object of the invention is to provide a spraybar having means for laterally dispersing fuel with minimal pressure losses therefrom.